Carburetor primer and throttle control mechanism



June 24, 1969 E. L. NELSON 3,451,383

CARBURETOR PRIMER AND THROTTLE CONTROL MECHANISM Filed OCt. 31, 1967 Sheet INVENTOR NELSON fi ujgzw aaLvl'tzil ATTORNEYS EUGENE L June 24, 1969 E. L. NELSON 3,451,383 CARBURETOR PRIMER AND THROTTLE CONTROL MECHANISM Filed Oct. 51, 1967 Sheet 2 f2 I32 F no.5 /4o I34 L/ i v hfi;in; 6. 6

w INVENTOR.

, EUGENE. L. NELSON 8o v, 54

76 72 ATTORNEYS United States Patent 3,451,383 CARBURETOR PRIMER AND THROTTLE CONTROL MECHANISM Eugene L. Nelson, Cedarburg, Wis., assignor to Tecumseh Products Company, Tecumseh, Mich., a corporation of Michigan Filed Oct. 31, 1967, Ser. No. 679,478 Int. Cl. F02m 1/16 US. Cl. 123187.5 7 Claims ABSTRACT OF THE DISCLOSURE An integrated throttle and primer control for a carburetor of a small internal combustion engine of the vertical crankshaft type wherein a throttle dial control knob supports a primer squeeze bulb and the knob is rotatably mounted by a shaft which also serves as a part of the pressure conduit between the primer bulb and carburetor. In addition, a coil spring received on the dial shaft retains the dial shaft axially in its mounting bracket and biases a positioning detent of the knob into engagement with the cooperating pocketed upper flange of the bracket.

An object of the present invention is to provide a con veniently arranged control mechanism for one-handed conjoint priming and controlling of the throttle and/or choke valves of the carburetor of a small internal combustion engine, such as the single cylinder two or four stroke cycle vertical shaft gasoline engine commonly employed on rotary lawn mowers.

Another object is to provide a control mechanism of the above character which is simple in construction and reliable in operation.

Other objects as well as features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a fragmentary top plan view of a single cylinder two stroke cycle engine equipped with the control mechanism of the present invention and mounted on the circular deck of a rotary lawn mower.

FIG. 2 is a fragmentary end elevational view of the engine and control mechanism of the invention looking in the direction of the arrow in FIG. 1, portions of the control mechanism being broken away to better illustrate detail.

FIG. 3 is a fragmentary top plan view of the throttlechoke control knob and primer bulb of the control mechanism.

FIGS. 4 and 5 are fragmentary horizontal sections taken on the lines 4-4 and 5-5 of FIG. 2, respectively.

FIG. 6 is a fragmentary end elevational view of the carburetor with a portion thereof broken away and shown in vertical section to illustrate the operation of the carburetor priming system.

Referring in more detail to the accompanying drawings, the integrated throttle-choke control and carburetor primer mechanism of the present invention is particularly adapted for use with a vertical shaft internal combustion engine such as the two stroke cycle single cylinder engine 10 shown herein mounted in the usual manner on the horizontal deck 12. of a rotary lawn mower or other powered appliance. Engine 10 has a crankcase '14 with a conventional diaphragm carburetor '16 mounted at one end thereof. A sheet metal air shroud 18 is fixed to the air shroud base 108 and encloses the flywheel and air fan mounted on the upper end of the crankshaft of the engine (not shown).

The throttle-choke dial control and primer assembly of the present invention comprises an upright hollow shaft 3,451,383 Patented June 24, 1969 20 journaled in bearings 22 and 24 of horizontal upper and lower flanges 26 and 28 respectively of a C-shaped sheet metal bracket 30 which is attached as by spot welding along its central portion 32 to the vertical side wall 33 of shroud 18. A molded plastic knob 34 slips onto the upper end of shaft 20 and the shaft is keyed by flats 36 and 38 to rotate with the knob. Snap rings 39 and 41 received in suitable grooves of shaft 20 axially retain knob 34 on the shaft. Knob 34 has a detent portion 40 dependent therefrom which, when the knob is rotated, is adapted to drop into one of a number of detent pockets, shown herein by way of example as five pockets 42, 44, 46, 48 and 50 (FIGS. 2 and 4) in upper flange 26, these pockets being properly oriented relative to knob 34 and the throttle and choke linkage to provide stop, idle, medium, full and start (choke) angular positions of shaft 20. These positions are visibly indicated to the operator by a pointer 52 (FIG. 3) 0n knob 34 which traverses a dial plate 54 attached as by spot welding to shroud 18 on which the names of these positions are imprinted as shown in FIG. 3.

Shaft 20 has an axial throughbore 60 forming a passageway communicating at its upper end with the sealed hollow interior of a squeeze bulb 62 which is secured to knob 43 by a resilient lip 64 at the lower open end of the bulb which snaps into an annular groove 66 of knob 34. The lower end of passage 60 receives a hose nipple adapter 68 secured therein as by a friction fit and which in turn receives one end of a flexible primer hose 70. Hose 70 is connected at its other end 72 to a nipple 74 of an elbow fitting 76 (FIGS. 2 and 6) secured to the cover plate 78 of the diaphragm chamber 80 of carburetor 16. Shaft 20 and hose 70 thereby establish communication between primer bulb 62 and the air chamber 82 beneath the regulating diaphragm 84 of the carburetor. Air chamber 82 is restrictedly vented to atmosphere by a calibrated hole 86 in plate 78.

The throttle-choke dial control linkage includes a crank arm 30 (FIGS. 2 and 5) having a squared hole 92 receiving the squared portion 94 of adapter 68 to key arm for rotation with adapter 68 and hence with shaft 20. A compression coil spring encircles shaft 20' and butts at its lower end against arm 90 and at its upper end against the lower flange 28 of bracket 30. Spring 100 exerts a downward force on shaft 20 to thereby yieldably urge detent 40 downwardly against flange 26 of bracket 30, thus permitting yieldably axial movement of shaft 20 to accommodate rotary movement of the detent from one pocket to another.

Arm 90 is connected by a link wire 102. and pivot screw clamp 103 to one end of a control lever 104 which pivots on a stud 106 secured to the underside of shroud base 108. The other free end 110 of lever 104 is disposed to selectively engage at the extreme limits of its travel the offset arm 112 on the choke shaft 114 (broken line position, FIG. 5) or a brass contact strip 105 (FIG. 5) connected by a lead 107 to the ignition system of the engine to function as a shorting switch through the ground connection provided by lever 104 (solid line position, FIG. 5). Throttle shaft 116 (FIG. 5) is actuated in a known manner by the conjoint influence of a flywheel air stream vane governor 118 and lever 104 through a yieldable biasing connection provided by a tension spring 120 and crank arm connector 122.

In operation, the carburetor throttle and choke valves may be manually set with the [fingers of one hand to their respective choke (start), full, medium, idle or stop positions (the last position also making the shorting-out connection with contact 105) by rotating control knob 34 until its pointer 52 points to the corresponding dial indicia imprinted on decal plate 54, thereby simultaneously rotating control shaft 20 and thus 3 pivoting lever 104- to suitably position the choke and throttle valves.

Simultaneously or sequentially, the carburetor may be primed by rapidly depressing bulb 62 With one finger. This pumps the air from the bulb via shaft 20 and hose 70 into the air chamber 82, thereby momentarily increasing the air pressure in chamber 82 faster than it can be relieved to atmosphere through vent 86. The increased air pressure in chamber 82 pushes the diaphragm 84 upwardly against the stern 124 of the fuel inlet valve 126 to thereby open this valve to admit fuel from the fuel line 1:28

to the fuel chamber 80 above diaphragm 84. The momentary pressure increase caused by squeezing bulb 62 also exerts, through diaphragm 84, a force on the fuel in chamber 80 which causes a check valve 130 in the fuel inlet fitting 132 to close. Hence fuel is forced from fuel chamber 80 via the fuel metering passage 134, past the back bleed check ball 136 in the main jet 138 of the carburetor, into throat 140 of the carburetor. As the air escapes through vent hole 86 in plate 78, the drop in air pressure permits diaphragm 84 to return to its normal position.

I claim:

1. In an engine having a carburetor with a fuel-air regulating valve therein, a linkage for controlling the position of said valve and priming means adapted to be actuated by a pulse of air pressure, the combintaion therewith of a control mechanism comprising a support connected to said engine, a shaft having an axial bore and being journaled in said support for rotation about the longitudinal axis of the shaft, a knob mounted on one end of said shaft for rotating said shaft, a flexible squeeze bulb mounted on said knob and having a hollow interior communicating with said bore of said shaft, a flexible conduit connected to the end of said shaft opposite said knob and connecting said shaft bore in communication with said primer means of said carburetor, and means interconnecting said shaft with said linkage such that the position of said valve is adjustable in response to rotation of said shaft by said knob.

2. The combnation set forth in claim 1, wherein said support comprises a C-shaped bracket having a central portion with a pair of arms extending transversely therefrom, said shaft being journaled in said arms, said knob having detent means engageable with cooperating detent means on one of said arms, and further including a coil spring encircling said shaft and engaging the other of said arms for yieldably urging said shaft axially in a direction to yieldably interengage said detent means of said knob and said one arm.

3. The combination set forth in claim 2 wherein said engine is mounted with its crankshaft vertical, said engine having -a flywheel mounted on the upper end of said crankshaft above the elevation of said carburetor and an air shroud enclosing said flywheel, said shroud having a vertical side wall, said central portion of said support bracket being secured to said side wall of said shroud with said bracket arms extending outwardly therefrom and oriented to support said control shaft in an upright position with said knob disposed generally flush with the upper surface of said shroud and with said flexible conduit and said linkage disposed below the elevation of said shroud.

4. The combination set forth in claim 3 wherein said knob has a pointer at the periphery thereof, and further including a decal means secured to said shroud adjacent the periphery of said knob with indicia thereon cooperating with said pointer to indicate the proper angular settings of said knob to obtain a selective setting of said valve of said carburetor.

5. The combination set forth in claim 4 wherein said knob detent means comprises a projection extending axially from the under side of said control knob and having a rounded nose, said cooperating bracket detent means comprising a series of half-round pockets formed in the upper one of said arms of said bracket complemental to said knob projection and arranged in the arcuate path of travel thereof to yieldably retain the knob in selective angular positions corresponding to those indicated by said pointer and cooperating decal means indicia.

6. The combination set forth in claim 3 wherein said shaft has an adapter secured to the lower end thereof connecting said flexible conduit to said shaft and providing communication between the bore of said shaft and the interior of said conduit, and wherein said linkage includes an arm received on said adapter and non-rotatably keyed thereto, said spring abutting at its lower end against said linkage arm and at said upper end aginst the lower one of said arms of said bracket.

7. The combination set forth in claim '1 wherein said carburetor comprises a diaphragm-type carburetor having a fuel chamber and an air chamber partitioned from one another by a regulating diaphragm and having a fuel inlet valve controlled by said diaphragm, said flexible conduit being connected to said air chamber, said :air chamber having a restricted air vent connecting the same to atmosphere, and a one way check valve in said carburetor disposed upstream of said fuel inlet valve and adapted to close the fuel inlet passageway :when the pressure of fuel downstream of said one way check valve exceeds the pressure upstream thereof.

References Cited UNITED STATES PATENTS 2,762,355 9/1956 Jones l23l80 2,986,135 5/1961 Clark et al. l23l80 3,345,045 10/1967 Tuggle 26l34 3,323,293 6/1967 Santi 123-1875 3,307,836 3/1967 Arndt et a1. 26l34 3,371,658 3/1968 Turner 123-1875 WENDELL E. BURNS, Primary Examiner.

US. Cl. X.R. 261-34 

